Scrambler – Hallo, thank you!
Not the upper value was too low, the lower was to high. Now it works like you thought it should work. May be due to my insufficient english skills. The Menue now no more jumps to the second line but of course it still jumps to the this .3 em padding.
If you by chance know anyone who knows anyone who knows anyone who knows where this breakpoint for switching to mobile menue is definded in the zillion lines of code or database I, if someone told me, just could change it.